Part Numbers for Koitos

In one thread we learned that the Toyota part number for the LHT 7" Koito is 90981-01037, and for the RHT version it's 90981-01035. In another thread we learned that the 200mm x 142mm LHT Koito is 90981-04011. Is the part number for the RHT version 90981-04008, and is 90981-04009 yellow?

In those threads both Koitos were described as being good lights. I'd like to know if Koito also made/makes good 165mm x 100mm and 5.75" four-light combinations, and, if so, what the part numbers are, and if they, too, are Toyota numbers. Thanks.

Be aware there is practically no such thing as a really good 5.75" or 165mm x 100mm H4 low beam. All of them are objectively deficient in their safety performance relative to the amount of light needed to see safely at normal roadway speeds. Some of them are frightfully deficient; others are merely "just deficient". Most sealed beams in those sizes are equally (but differently) deficient. Sometimes the realities of the application mean having to pick the least-deficient available lamps and do everything possible to optimize their performance (bulb selection, low-loss feed and ground, precisely correct aim).

The 200mm x 142mm RHT Koito H4 headlamp is indeed Toyota #90981-04008. It's certainly a very decent lamp. I like its performance better than the Hella, and would put it about on par with (though photometrically different from) the Cibie. The 90981-04009 was the same lamp but with a yellow-balloon H4 bulb installed instead of a plain H4.

I have the Toyota part numbers for the smaller round and rectangular lamps somewhere, but I'm afraid I can't find them right now. I don't find it cost-effective to chase after expensive OE Toyota lamps that aren't better than the decent-to-excellent options in those sizes.

Be aware there is practically no such thing as a really good 5.75" or 165mm x 100mm H4 low beam.

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<chuckle> Memory flash: Mechanix Illustrated test of the 1962 Impala Sport Coupe: Four years after the 1958 sea change, Tom McCahill could be heard grousing "I still say two good headlights are better than four lousy ones!" Funny how you brought that back.

At times I still miss my 1969 Chevy half ton. I had 7" Cibie H4 lights, plus I added a pair of 5-3/4" Cibie H1 high beams in a pair of Unity buckets from old spotlights. Good light. The Unity spotlight in the center of the roof with the #4537 landing light was handy, too.

Given that a 5-3/4" high/low has half the reflector area of a 7" lamp, I understand why the small ones just don't make the cut. Also, I've gathered here that the low beam-only Hella BiFocus is the best option for a 5-3/4" low beam. It sounds like a person stuck with 5-3/4" high/low should go with Cibie or Koito, with Hella and Bosch following somewhere behind.

In most cases, is it simply small reflector and not enough light? Is the general beam pattern OK on some of these lamps? If the pattern is good, another pair of same, mounted as auxiliaries, with all four aimed carefully, should theoretically give a decent low beam, more or less equivalent to what you might get from a pair of 7" lamps. Right???

Hamilton Felix said:

<chuckle> Memory flash: Mechanix Illustrated test of the 1962 Impala Sport Coupe: Four years after the 1958 sea change, Tom McCahill could be heard grousing "I still say two good headlights are better than four lousy ones!" Funny how you brought that back.

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Yeah, I remember that, too. Mr. McCahill was certainly full of sh...arply-expressed opinions, often with no basis in fact.

I've gathered here that the low beam-only Hella BiFocus is the best option for a 5-3/4" low beam.

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I'd agree with that, if we're talking about halogen lamps.

It sounds like a person stuck with 5-3/4" high/low should go with Cibie or Koito

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I don't recall the Koito 5 3/4" H4 being particularly special. Neither is the Cibie, but in the case of the Cibie the other commonly-available major-brand options (Bosch, Hella) are worse. The Marchals were better than the Cibies, but they haven't been made in years.

In most cases, is it simply small reflector and not enough light?

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Yes.

another pair of same, mounted as auxiliaries, with all four aimed carefully, should theoretically give a decent low beam, more or less equivalent to what you might get from a pair of 7" lamps. Right???

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No. You'd wind up with way too much foreground light and still have severely inadequate seeing distance.

No. You'd wind up with way too much foreground light and still have severely inadequate seeing distance.

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Well darn, no easy answers for small halogen lights.

BTW, using my StarrHID headlights in snow emphasized the foreground effect. A white road surface throws back a lot more light than a dark one, making it harder to see in the distance.